Composite material, method for preparing the same and application of the composite material in negative electrode of lithium ion battery

Abstract

The application discloses a composite material and a preparation method and application thereof in a lithium ion battery negative electrode. The titanium nitride / carbon nanotube composite material comprises zero-dimensional TiN nanoparticles and one-dimensional carbon nanotubes, and the zero-dimensional TiN nanoparticles are anchored on the one-dimensional carbon nanotubes to provide active sites. The titanium nitride / carbon nanotube composite material is added into the lithium ion battery negative electrode as a functional additive, and the electrochemical performance of the lithium ion battery is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a titanium nitride / carbon nanotube composite material, its preparation method, and its application in lithium-ion battery anodes. By doping with a specific composite conductive agent (TiN@CNTs) to optimize the internal conductive network of the electrode, the high-rate cycle performance of the battery is significantly improved. Background Technology

[0002] With the increasing market demand for fast charging capabilities of lithium-ion batteries, the development of batteries with excellent high-rate performance has become a research hotspot. Silicon-based materials (such as Si, SiO2) are being utilized. x Due to its extremely high theoretical specific capacity (~4200 mAh / g), it is considered the first choice for the next generation of high energy density anodes. However, its huge volume change (>300%) leads to the pulverization of active material, loss of electrical contact with current collector, and continuous damage and reconstruction of SEI film, consuming electrolyte and active lithium, resulting in rapid capacity decay. This problem is particularly fatal under high-rate charge and discharge conditions.

[0003] The traditional approach is to mix it with graphite and add conductive agents (such as acetylene black or Super P). However, traditional carbon black conductive agents have zero-dimensional point contacts, resulting in a fragile conductive network that is easily destroyed during the expansion / contraction of silicon volume, leading to a continuous increase in electrode resistance. Although one-dimensional materials such as carbon nanotubes (CNTs) can construct more stable conductive networks, their contact with active particles is insufficient, and their improvement on ion transport is limited.

[0004] Titanium nitride (TiN) is a metal with high electrical conductivity (~10⁻⁶ Ω·cm). 4 TiN nanoparticles are ceramic materials with excellent electrochemical stability (S / cm) and a certain affinity for lithium ions. However, they are prone to agglomeration and are difficult to disperse uniformly in electrodes.

[0005] Therefore, the key to solving the bottleneck of high-rate performance of silicon-based anodes is to construct a highly stable three-dimensional conductive network that can conduct electricity, promote ion transport, and adapt to volume changes. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a negative electrode material formulation and preparation method that can significantly improve the cycle stability of lithium-ion batteries, especially silicon negative electrode batteries, under high-rate charge-discharge conditions.

[0007] The first aspect of this invention provides a titanium nitride / carbon nanotube composite material (TiN@CNTs) and a method for preparing the same.

[0008] The titanium nitride / carbon nanotube composite material (TiN@CNTs) provided by the present invention includes zero-dimensional TiN nanoparticles and one-dimensional carbon nanotubes, wherein the one-dimensional carbon nanotubes serve as a flexible framework to construct long-range electronic conduction pathways; and the zero-dimensional TiN nanoparticles are anchored on the one-dimensional carbon nanotubes to provide active sites.

[0009] In the composite material, TiN accounts for 10-50% by mass, specifically 30%.

[0010] The carbon nanotubes are multi-walled carbon nanotubes.

[0011] In the described titanium nitride / carbon nanotube composite material, one-dimensional CNTs serve as a flexible framework, constructing long-range electronic conduction pathways and effectively bridging active zero-dimensional TiN nanoparticles. The zero-dimensional TiN nanoparticles anchored therein provide numerous active sites, forming tight "point" contacts with the active material, significantly reducing contact resistance. Furthermore, the 3D conductive network constructed by the titanium nitride / carbon nanotube composite material exhibits excellent mechanical toughness, capable of adapting to volume changes in silicon without cracking.

[0012] The above-mentioned titanium nitride / carbon nanotube composite material (TiN@CNTs) was prepared by a method including the following steps: 1) Carbon nanotubes (CNTs) are acidified to enrich their surface with carboxyl and hydroxyl functional groups; 2) Disperse the treated CNTs in a solvent, add a titanium source, and stir vigorously to ensure full adsorption; 3) Adding deionized water causes the titanium source to hydrolyze on the CNTs surface, forming a TiO2 sol-coated CNTs precursor (TiO2@CNTs). 4) The obtained precursor was calcined in an ammonia atmosphere to nitride TiO2 into TiN, yielding the final product TiN@CNTs.

[0013] In step 1) of the above method, carbon nanotubes are treated with a mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) to generate hydroxyl and carboxyl groups on their surface. The ratio of mixed acid to carbon nanotubes can be 20-100 mL : 100-500 mg; The temperature can be 60-80℃, and the time can be 2-6 hours; In step 2) of the above method, the titanium source may specifically be at least one of tetrabutyl titanate, tetramethyl titanate, tetraethyl titanate, and tetraisopropyl titanate. The solvent may be ethanol; The mass ratio of the titanium source (calculated as titanium) to the treated CNTs is 1:5 to 1:20; In step 3) of the above method, the amount of deionized water added is 20-100 mL / g relative to the mass of the titanium source (calculated as titanium). The hydrolysis temperature is room temperature to 60°C, and the time is 1 to 6 hours.

[0014] In step 4) of the above method, the calcination temperature can be 500~700℃ and the time can be 2~5 hours.

[0015] The application of the aforementioned titanium nitride / carbon nanotube composite material (TiN@CNTs) as a functional additive in lithium-ion battery anode materials also falls within the scope of protection of this invention.

[0016] In the aforementioned application, the lithium-ion battery may specifically be a silicon anode lithium-ion battery.

[0017] A second aspect of the present invention provides a negative electrode and a method for preparing the same.

[0018] The negative electrode provided by this invention includes a current collector and a negative electrode slurry, wherein the negative electrode slurry is composed of the following components by mass percentage: Negative electrode active material: 92%~97%, conductive agent 1%~2%, TiN@CNTs composite material 0.5%~5% (specifically 0.5%~3%, more specifically 3%), binder 1%~2%, and thickener 0.5%~1%; This invention optimizes the internal conductive network of the electrode by doping TiN@CNTs composite material with a conductive agent, thereby significantly reducing DCR and improving battery energy efficiency and high-rate cycling performance.

[0019] The negative electrode active material comprises 5% to 20% silicon oxide (SiOx) material and the balance being graphite; The conductive agent may specifically be Super P; The adhesive may be selected from at least one of PAA and sodium alginate; The thickener may be CMC.

[0020] The negative electrode is prepared by a method including the following steps: 1) Dry mix the negative electrode active material, conductive agent, and TiN@CNTs composite material evenly; 2) Add the binder, thickener, and deionized water solution, and vacuum stir to form a slurry; 3) Coat the obtained slurry onto a metal foil, dry, roll, and cut to obtain the final product.

[0021] The present invention also provides a lithium-ion battery.

[0022] The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte; The negative electrode is the negative electrode of the above-mentioned TiN@CNTs composite material.

[0023] Compared with the prior art, the present invention has the following significant advantages: (1) Synergistic construction of a “rigid and flexible” 3D conductive network: One-dimensional CNTs serve as a flexible framework, constructing long-range electronic conduction paths and effectively bridging active particles; zero-dimensional TiN nanoparticles anchored on them provide a large number of active sites, forming tight “point” contacts with the active material, greatly reducing contact resistance. This network has excellent mechanical toughness and can adapt to changes in the volume of silicon without breaking.

[0024] (2) Improved ion transport kinetics: TiN has a certain adsorption and transport capacity for lithium ions. Its introduction effectively reduces the ion migration impedance of the electrode and accelerates the charge and discharge rate.

[0025] (3) Promotes the formation of a stable SEI film: The uniform conductive network ensures uniform current distribution and avoids excessive SEI film growth caused by excessive local current. The good stability of TiN also helps to form a denser and more stable interface film.

[0026] (4) Significantly improve electrochemical performance: Experiments show that the SiOx-graphite anode doped with 3% TiN@CNTs can be cycled for more than 1500 cycles at a high rate of 1P in a large energy storage cell. Attached Figure Description

[0027] Figure 1 This indicates the cycle life at 45°C of batteries made by adding the composite materials obtained in Examples 2-4 and Comparative Example 1, respectively.

[0028] Figure 2 This indicates the cycle life at 25°C of batteries made by adding the composite materials obtained in Examples 2-4 and Comparative Example 1, respectively. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0031] Example 1: Preparation of TiN@CNTs composite material Multi-walled carbon nanotubes were treated with a mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) (treated at 70℃ for 4 h, with a mixture of acid and carbon nanotubes at a ratio of 50 mL: 200 mg) to generate hydroxyl and carboxyl groups on their surface. The treated CNTs were dispersed in 100 mL of ethanol, and 2.0 g of tetrabutyl titanate was added as a titanium source. The mixture was stirred vigorously for 2 h to allow for full adsorption (at this time, the mass ratio of titanium to CNTs was approximately 1:10). Under the conditions of 40℃ water bath and stirring, 10 mL of deionized water was slowly added dropwise to hydrolyze tetrabutyl titanate on the surface of CNTs for 2 h to form TiO2 sol-coated CNTs precursor (TiO2@CNTs). The precursor was calcined at 550°C for 3 hours under an ammonia atmosphere to nitride TiO2 into TiN, yielding the final product TiN@CNTs; the mass percentage of TiN in the final product was approximately 30%.

[0032] TEM characterization showed that TiN nanoparticles were uniformly anchored on the surface of carbon nanotubes, with a particle size distribution of 5-20 nm. Thermogravimetric analysis (TGA) determined that TiN accounted for approximately 30% of the final product by mass.

[0033] Example 2: Preparation of a negative electrode with 1 wt% TiN@CNTs doping Preparation of negative electrode slurry: Active material: 94.5 wt% (of which SiOx: 10% and artificial graphite: 84.5%) Super P: 1.5 wt% TiN@CNTs: 1 wt% PAA adhesive: 2 wt% CMC: 1 wt% First, the negative electrode active material, Super P, and TiN@CNTs are dry-mixed evenly. Then, a deionized aqueous solution containing PAA and CMC is added, and the mixture is stirred under vacuum to form a slurry. The resulting slurry is coated onto a metal (copper) foil, dried, rolled, and cut to obtain the final product.

[0034] Example 3: Preparation of a negative electrode with 3 wt% TiN@CNTs doping Preparation of negative electrode slurry: Active material: 92.5 wt% (of which SiOx: 10%, artificial graphite: 82.5%) Super P: 1.5 wt% TiN@CNTs: 3wt% PAA adhesive: 2 wt% CMC: 1 wt% First, the negative electrode active material, Super P, and TiN@CNTs are dry-mixed evenly. Then, a deionized aqueous solution containing PAA and CMC is added, and the mixture is stirred under vacuum to form a slurry. The resulting slurry is coated onto a metal (copper) foil, dried, rolled, and cut to obtain the final product.

[0035] Example 4: Preparation of a negative electrode with 5 wt% TiN@CNTs doping Preparation of negative electrode slurry: Active material: 90.5 wt% (of which SiOx: 10% and artificial graphite: 80.5%) Super P: 1.5 wt% TiN@CNTs: 5wt% PAA adhesive: 2 wt% CMC: 1 wt% First, the negative electrode active material, Super P, and TiN@CNTs are dry-mixed evenly. Then, a deionized aqueous solution containing PAA and CMC is added, and the mixture is stirred under vacuum to form a slurry. The resulting slurry is coated onto a metal (copper) foil, dried, rolled, and cut to obtain the final product.

[0036] Comparative Example 1 Without adding TiN@CNTs, the content of the conductive agent Super P was increased to 2.5 wt%, and the remaining steps were the same as in Example 2.

[0037] Battery Assembly and Testing: The negative electrode, separator (polypropylene three-layer composite separator), positive electrode (lithium nickel cobalt manganese oxide positive electrode), and electrolyte (1M LiPF6 in EC:EMC:DMC (volume ratio 1:1:1), containing 2% VC additive) of the examples and comparative examples were assembled into batteries. 25℃ and 45℃ 1P / 1P cycle tests and DCR (1C, 30S, 50% SOC) tests were conducted at constant temperatures of 25℃ and 45℃.

[0038] The test results are shown in Table 1.

[0039]

[0040] The results show that the anode doped with 3% TiN@CNTs (Example 3) exhibits the best overall performance. Compared to Comparative Example 1 without the addition of this composite material, its DC internal resistance (DCR) is reduced by 12.6%, its energy efficiency is improved by 1.6 percentage points, and its cycle life at 25℃ and 45℃ is significantly improved by approximately 95% and 86%, respectively. This indicates that an appropriate amount of TiN@CNTs composite material can synergistically construct a stable three-dimensional conductive network, significantly improving the structural stability of the electrode and its electrochemical kinetic performance at high rates, effectively suppressing capacity decay. Therefore, this invention provides an efficient and feasible solution to the cycle life problem of silicon-based anodes at high rates by doping with a specific proportion of TiN@CNTs composite material.

[0041] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A composite material comprising zero-dimensional TiN nanoparticles and one-dimensional carbon nanotubes, wherein the one-dimensional carbon nanotubes serve as a flexible framework to construct long-range electron conduction pathways; and the zero-dimensional TiN nanoparticles are anchored on the one-dimensional carbon nanotubes to provide active sites. In the composite material, TiN accounts for 10%-50% by mass.

2. A method for preparing the composite material according to claim 1, comprising the following steps: 1) Carbon nanotubes (CNTs) are acidified to enrich their surface with carboxyl and hydroxyl functional groups; 2) Disperse the treated CNTs in a solvent, add a titanium source, and stir vigorously to ensure full adsorption; 3) Adding deionized water hydrolyzes the titanium source on the surface of carbon nanotubes (CNTs) to form a TiO2 sol-coated CNT precursor (TiO2@CNTs). 4) The obtained precursor was calcined in an ammonia atmosphere to nitride TiO2 into TiN, yielding the final product TiN@CNTs.

3. The method according to claim 2, characterized in that, In step 2), the titanium source is at least one of tetrabutyl titanate, tetramethyl titanate, tetraethyl titanate, and tetraisopropyl titanate. The solvent is ethanol; The mass ratio of the titanium source (calculated as titanium) to the treated CNTs is 1:5 to 1:

20.

4. The method according to claim 2, characterized in that, In step 3), the amount of deionized water added is 20 ~ 100 mL / g relative to the mass of the titanium source (calculated as titanium); The hydrolysis temperature is room temperature to 60°C, and the time is 1 to 6 hours.

5. The method according to claim 2, characterized in that, In step 4), the calcination temperature is 500-700℃ and the time is 2-5 hours.

6. The application of the composite material described in claim 1 as a functional additive in lithium-ion battery anode materials.

7. The application according to claim 6, characterized in that, The lithium-ion battery is a silicon anode lithium-ion battery.

8. A negative electrode, comprising a current collector and a negative electrode slurry, said negative electrode slurry comprising the following components in weight percentage: Negative electrode active material: 92%~97%, conductive agent 1%~2%, composite material as described in claim 1 0.5%~5%, binder 1%~2% and thickener 0.5%~1%.

9. The negative electrode according to claim 8, characterized in that, The negative electrode active material comprises 5%~20% silicon-oxygen SiOx material and the balance being graphite; The conductive agent is Super P; The adhesive is selected from at least one of PAA and sodium alginate; The thickener is CMC.

10. A lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode and an electrolyte; in, The negative electrode is the negative electrode as described in claim 8 or 9.

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